The use of phenol formaldehyde type resins for curing rubbers is well known in the art. Typically, a metal oxide and metal salt—in particular, a metal halide—is used as an activator for the resin curative. There have been various attempts to modify this cure system in order to improve performance of the resulting rubber or rubber composition. For example, U.S. Pat. No. 4,707,519 discloses the use of a phenolic resin with p-toluenesulfonic acid as an activator. U.S. Pat. No. 4,835,204 discloses the use of salicylic acid as an activator with phenolic resins in forming thermoplastic vulcanizates (cured rubber/thermoplastic blend). U.S. Pat. No. 5,196,462 discloses the use of zinc-mercapto compounds as activators with phenolic resins. U.S. Pat. No. 5,457,159 uses sodium bisulphite as an activator with phenolic reins. U.S. Pat. No. 5,952,425 uses phenolic resins having high levels of dibenzyl ether linkages relative to the more conventional phenolic resin with mostly methylene linkages, which were found to be more active as curing agents. U.S. Pat. No. 6,143,828 discloses that phenolic resins with only a metal oxide can achieve a partial cure state in rubber/thermoplastic TPEs. U.S. Pat. No. 6,437,030 discloses a phenolic resin as a curative with a metal halide and metal carboxylate compound. Finally, EP 1 433 812 A discloses the use of boranes and metal oxides with phenolic resins to form partially cured TPVs.
What is needed is a curative that uses the well known phenolic resins while achieving a high level of cure. Also, the presence of halogen salts in the rubber makes the composition hygroscopic, thus necessitating the need to dry the rubber at some stage before it is used. The present invention solves these and other problems.